Gas-filled display device having capacitive envelope



United States Patent 169TV,171, 248; 313/108,204, 210, 325, 329,153(Cursory), 161(Cursory), 201; 178/7.3 (D & Advisory); 340/324, 324.1,343, 344

56 References Cited UNITED STATES PATENTS 2,925,530 2/1960 Engelbart 3 l5/84.6

[72] Inventor George E. Holz 2,933,648 4/1960 Bentley 315/169 NorthPlainfield, NJ. 2,967,965 l/1961 Schwartz 315/169X [2]] Appl. No.668,290 3,042,823 7/1962 Willard 315/169X [22] Filed Sept. 11,19673,157,824 11/1964 Jones 315/169 [45] Patented Dec. 29, 1970 3,206,6389/1965 Moore 315/169X 73] Assignee Burroughs Corporation 1,676,7907/1928 Mailey 3 13/201 Detroit, Mich. 2,624,858 1/1953 Greenlee 313/201a corporation of Michigan 2,629,839 2/1953 Greenlee 313/201 2,943,2236/1960 Fay 313/201 3,258,644 6/1966 Rajchman 315/169X 1. 1 GAS-FILLEDDISPLAY DEVICE HAVING 3,050,654 8/1962 Toulon 315/169X I CAPACITWEENVELOPE Primary Examiner James W Lawrence 3 7 Drawing AssistantExaminerDavid OReilly [52] us. Cl. 313/204, A"0meys |(enneth L. Millerand Robert A Green 313/210, 315/169 [51 1 Int. Cl; ..H0lj 17/04, H01j61/04 [50] Field of Search 315/169,

ABSTRACT: The disclosure is of a gas plasma cell having electrodecarrying end walls of a material having a high dielectric constant,greater than that of glass, so that the cell has high capacitance. Thedisclosure is also of a matrix of such cells and combinations of suchcells and other cells having lower capacitance.

SUSTAIN SUSTAIN I I I l c 2/0 229' FIRE FIRE I r 1' I I I (229 224 22s22? 1 PATENIEDnEmm SHEET 1- OF v Ma/5m ATTORNEY FBG4 . 1v GAS-FILLEDDISPLAY nEvrCE-nAvmo CAPACIT I ENVELOPE BACKGROUND OF INVENTION Thepresent invention relatesto a gas plasma cell made of glassandcontaining a gas which is adapted to glow when a operatingpoten tialis applied between electrodes on the end walls of the cell. The'cellhasthe characteristic that,..when glow is produced, electrical charges aregenerated and stored on the end walls of the cell, and the glow can besustained by the application of sustaining potential which may besmaller than thefiringpotential. Known gas plasma cells normally havesmall capacitance, and this characteristic imposes certain limitationson the operation and utility of the cells.

' functions.

' BRIEF oas calrriouorraa DRAWING In the drawing: I FIG. I is asectional elevationaluview of a light-producing cell embodying theinventionand a circuit in which it may be operated; f FIG. 2 is asectionalelevationaljview of a portion of a modification of theinvention;

FIG. 3 is a sectional elevational view of a modification of theinvention;- 1

FIG. 4 is a sectional 'elevational view of amo'dificati'on of the deviceof FIG. 3; I

FIG 5 is a perspectiveview of a device embodying the invention andschematic representationof a circuit in which it maybedperated; I

FIG. 6 is a sectional elevational view of a modification of theinvention and a schematic representation of a circuit in which it may beoperated; and

FIG. '7 isja sectional elevational view of a modification of theinvention and schematic representation of a circuit in which it may beoperated. g

DESCRIPTION'OF THE PREFERRED EMBODIMENTS Apparatus l0 embodying theinvention comprises a cell formed'of insulating material such as glassandincluding a hollow cylindrical envelope having end walls and whichform a gastight seal therewith. According to the invention, discs orplates and of a material having a relatively high dielectric constant,called K, are secured to the end walls 30 and 40, respectively, andelectrodes and 80, respectively, are secured in turn to the discs 50 and60. The discs 50 and 60 increase the capacitance of the cell to afavorably high level, and they may be of any suitable material, forexample, a ceramic such as barium titanate. The discs may also be of anyconvenient thickness. It is clear, of course, that glass walls 30 and 40may be omitted and discs 50 and 60 can themselves comprise end walls tocell 10, as shown in part FIG. 2. Glass typically has a dielectricconstant of 7s, and .plates 50 and 60 preferably are in the range ofabout 400m about 29006,.

The cell 10 includes an ionizable gas which can be fired and caused toflow and maintain the glow when a suitable sustaining voltage is appliedto it. Suitable gases are argon, neon, krypton, nitrogen," helium, etc.,or mixtures'of these gases.

Mixtures of neon and nitrogen are effective, and a mixture of A typicalcircuit for operating cell 10 includes, in series, a source ofsustaining potential, a source of firing pulses, and an impedance, forexample, a resistor connected between contacts 70 and 80. Outputterminals are provided on resistor 120. Operating parameters aredetermined generally by the size of the cell, the gas content, and thelike, and for a cell having a thickness of a few mils and with aneonnitrogen gas mixture, the sustainingpotential produced by source 100is an alternating signal of about 700 volts and a frequency of about 500kc., and the firing signal produced by source 110 is a pulse of about tI00 volts.

In one mode of operation of the cell 10, a sustaining signal is appliedbetween electrodes 70 and 80 from source 100, and at a selected time afiring pulse from source 110 is also applied. This combination ofvoltages causes the gas within the cell to ionize and glow, and the glowcan be sustained by the sustaining potential. Due to the relatively highcapacitance of the cell, when the cell fires, a'usable current pulse canbe detected in resistor 120. The cell may also be operated by firstapplying a firing pulse of sufiicient amplitude and then sustaining theglow by the application of the sustaining potential.

Due to the relatively high capacitanceof the cell, the cell exhibits amore intense or brighter glow at a selected operating frequency thanwould have been exhibited by cells of the prior art at the samefrequency.

In a modification of the invention shown in FIG. 3, a display panel isprovided which includes a plurality of cells 10 of the type describedabove. In this case, it may be desirable to have the regions or bodies50 and 60'of high dielectric material of one cell mechanically isolatedfrom those of adjacent cells, as shown, to maintain electrical isolationbetween cells. It may be desirable for bodies 50 and 60 to have a largerdiameter than the gas-filled volume of the cell as shown in FIG. 1, forexample. The panel 150 may be made in relatively simple fashion fashionby assembling a sandwich of glass plates including an apertured centralplate and top and bottom glass plates and 180. The individual bodies ofhigh dielectric material 50 and 60 are secured to the top and bottomglass plates in vertical alignment with apertures in the central plate,and the individual contacts 70 and 80 aresecured to the bodies 50 and60. Separate electrical connec- 'tions including output resistors 120may be made to each cell through contacts 70 and 80 each cell, and eachcell may be operated individually to record intelligence and to displaya light pattern.

In an alternative construction, shown in FIG. 4, the end walls of thecells themselves comprise the bodies 50 and 60 of high K materialwithout an intervening plain glasslayer being provided. This type ofcell may also be made in the manner described above, with plates 170 andbeing apertured and bodies 50 and 60 comprising inserts, or it may bemade by embedding individual glass cells having bodies 50 and 60 as endwalls in a suitable support medium of a synthetic resinous material.

Electrical connections may also be made as shown in FIG. 5. Assumingthat the cells in panel 150 are arrayed in rows and columns, a singlerow lead 200 may be connected to each row of contacts 70 on the topsurface, and a single column I ead 206 may be connected to eachcolumn'of contacts 80 on the bottom surface. An output impedance 120 isalso provided for each cell in either its row or column conductor. Asis' well known with matrix-type devices such as this, an input signalapplied to one row lead 200 and one column lead 206 will cause onecell-to glow where the leads cross. Thus, the panel 150 as shown in FIG.5 can be used to record intelligence in many different ways. Forexample, if a cell is on and is being sustained and has a firing signalapplied to it, it will not change state and no current pulse will bedetected in the associated resistor 120. Or, if a cell has sustainingsignal applied to it but is not on, a firing pulse is applied and itturns on, then a detectable signal canfbe derived from the associatedresistor I20. Operations of this type can be used in electronic logicsystems to process information. Systems and methods for using the panel150 in logic operations will occur readily to those skilled in the art.

Another unique embodiment of the invention is shown in FIG. 6 andcomprises a cell pair including a first cell 210 having an envelope andend walls of low K glass, known as a low K cell, which is coupled to asecond cell 220 of the type described above and known as a high K cellwhich has end walls 221 and 222 of material having high dielectricconstant. In the simplest arrangement, one cell of each type is providedand both cells are formed in a single glass panel in operative relationwith each other. Operative relation means that the cells are closeenough to each other so that, when one generates ultraviolet light, thelight can penetrate to and affect the operation of the other. Cell 210has end electrodes 223 and 224, and cell 220 has end electrodes 225 and226.

In one mode of operation of the cell pair, both cells 210 and 220 havesustaining potential applied to them from sources 227 and 228,respectively, and the low K cell 210 is fired by the application of afiring pulse from source 229. The firing of cell 210 generatesultraviolet light which is coupled to cell 220 through the glass betweenthem. This radiation generates photoelectrons in cell 220 which, actingin the applied electric field, causes cell 220 to fire and generate avisual output and an electrical output in resistor 120. The cell pair inthis case may be considered to be an amplifier.

The reverse operating sequence may be employed with cell 220 turning oncell 210 by means of ultraviolet light. Or in still another mode ofoperation (FIG. 7), the high K cell 220 may be coupled through itsoutput impedance by leads 230 to one or more low K cells 210, and therelatively large electrical output of the cell 220, when it is fired,can be used to fire the low K cells 210.

Of course, it is clear that the required synchronization between thevarious signals and the ultraviolet light is"'r' 'rovided. in addition,different numbers of the two types of cells may be provided as requiredby a particular application.

1. A display panel including a gas filled cell having low capacitanceand a gas-filled cell having high capacitance, circuit means coupled toeach cell for firing the cell, said cells being coupled in closerelationship so that the firing of one facilitates the firing of theother 2. The panel defined in claim 1 wherein said cells are positionedclose together so that ultraviolet light generated by one when it firescan be transmitted to the other to facilitate its fir- 3. The celldefined in claim 1 and including an output impedance in the circuit ofsaid high capacitance cell and leads coupling said output impedanceacross said low capacitance cell.

